Furnace



y 7 D. J. LUTY 2,086,812

v FURNACE 7 Filed March 17, 1935 v 2 Shee"tsSheet 1 \GNiTION DEVKZE \menm D. J. LUTY July 13, 1937.

FURNACE Filed March 17, 1935 2 Sheets-Sheet 2 mmm) Patented July 13, 1937 UNITED STATES PATENT. OFFICE FURNACE Donald J. Luty, Detroit, Mich., assignor to Wood Hydraulic Hoist & Body Company, Detroit, Mich., a corporation of Michigan Application March 17, 1933, Serial No. 661,256 16 Claims. (01'. 110-49) This invention relates to recirculation control of burned gas in producing combustion. 'The invention is especially applicable to oil burners, and particularly to oil burners used to heat furnaces although it is conceived that the use and control of burned gases of combustionrecirculated to the flame may be useful in other flames than oil burners. a,

In the burning of oil forfuel in furnaces or boilers it is necessary to provide air to be mixed with the oil so that combustion can occur and it has been found that use of burned gases from the combustion,circulated and controlled and mixed with the combustible mixture has many :advantages. Mixing burned gas with the oil and air in the combustible mixture has the result of enlarging the flame and reducing its temperature. Such a fla'me is termed a blue flame as distinguished from the luminous flame which occurs when the combustible mixture consists only of oil and fresh air. This blue flame, burning in the presence of a forced current of air-mixed with burned gas, burns with substantially no noise whereas the luminous flame produces a consider- -able noise in its combustion which has been greatly objectionable when used in a home heating equipment.

Because the blue flame is of greater size than the luminous flame its heat is distributed over a greater area within the combustion chamber which has the desirable result of even heat dis tribution. Ihe blue flame is of lower temperature than the luminous flame which considerably reduces the deterioration of the walls of the combustion chamber in which it burns andpermits the practical use 'of a metal combustion chamber. Although the blue flame is of lower temperature, the fact that it is of greater size than the luminous flame causes it to produce the same amount ofaggregate heat as the luminous flame with the same amount of fuel consumed. The blue flame also largely eliminates carbon deposit within the furnace owing to the fact that no free carbon is produced in the process of combustion. This fact is attested by the absence of luminosity ordinarily produced by free carbon rendered incandescent by the heat of combustion. I

The blue flame is produced by mixing with the air and oil a controlled quantity of gas having no oxygen or a low oxygen content which may be conveniently obtained in the form of the burned gases of combustion from the flame which are recirculated from the gas flues of the furnace back into the combustion chamber, preferably by the ,same means as is used to produce the fresh air current. The flame can only burn in the presence of a predetermined proportion .of burned gas in the mixture and if an excess amount of burned gas is used the flame will expire and therefore, if it is desired to mix a considerable quantity of burned gas with the combustible mixture the to various degrees of pressure, both above and below atmospheric pressure, it is evident that 'a mere flxedorifice to admit the recirculated gas from the gas flues to the combustion. chamber will not suffice and that automatic means must be provided which will compensate for the variations in pressure in the gas flues.

This invention provides means for automatically maintaining a predetermined proportion of air and burned gas supplied to the combustion chamber and mixed with oil under normal combustion conditions. It also provides means to preventvan excess amount of burned gas being supplied under abnormal conditions. It also provides means for supplying air without burned gas at, and shortly following, the instant of ignition which assures ignition taking place and combustion being established. The invention provides various means of adjustment to compensate for varying draftconditions and other variable conditions and also provides various other new, and useful features of construction and arrangement as hereinafter more fully described and particularly pointed out in the claims, reference being had to the accompanying drawings, in which, v

, Fig. 1 is a longitudinal vertical section through a boiler equipped with this invention, the attachment forming the control mechanism of my invention being shown in elevation.

Fig. 2 is a front elevation of the boiler shown in Fig. 1, parts being broken away and in section for-better disclosure.

Fig. 3 is a fragmentary enlarged vertical section through the air inlet and combustion gas conduit leading to the motor driven fan. which forces the mixture of air and gases of combus-' tion into the combustion chamber.

Fig.4 is an elevation of the lower portion of the combustion gas conduit, partially in section,

' result.

leverflxed in another position for a different Like reference characters refer to like parts in the different figures of the drawings.

The heat unit, indicated at I, is a boiler having an inner horizontal combustion chamber 2 a where the fuel is burned, from which down draft es 3 for the .products of combustion extend vertically between cross conduits 4 in which is'water, the products of combustion passing to a horlzontalflue 5, from which part of the same may pass outwardly through a smoke pipe '5. This construction in general is like that shown in the patent to Jerome No. 1,804,777, issued tion, is pumped to a mixing chamber at the entrance of the combustion chamber through a pipe I passing through a larger passage 8 in a conduit 9 which joins with a housing II) at the upper end of a vertical conduit -I I which, at its,

lower end, connects with a fan housing I2. An electric motor I3 has a rotary fan I4 on its shaft I 3a within the housing I2 for forcing and blowing air, and as will hereafter appear, some of the gaseous products of combustion are drawn from the'flue 5 to be mixed with air and fuel to provide a combustible mixture which burns in the combustion chamber 2.

The conduit for air and the recirculated portion of the gaseous products of combustion is a vertical pipe I5, the upper end of which has an'outlet I I5 around the shaft I3a of the motor to lead intothe interior of the fan housing I2. At its lower end the pipe conduit I5 is formed .with 'a rectangular box I5a, which is connected by a pipe or conduit I! with one end of the flue 5 previously described, from the other end of which the smoke pipe 6 extends.

In a side of the conduit I5 an air opening I8 is made. In'the lower part I5a a vane I 9 is suspended from a rock shaft 20. I3 is rectangular and its top and vertical edges lie close to the adjacent sides of the box I5o to prevent substantial passage of gas while its lower edge is spaced from the bottom of the box. At oneouter end of the shaft 23 a lever 2i, having a weight 22 adjustably mounted thereon, is located, the lever being mounted for rotat able adjustment on the shaftfor'purposes hereafter describedr.

Supporting rods 23 are rigidly connected at their lower ends to the vane I9 and at their upper ends pass through the opening I8 and carry a closure plate or air valve 24 slightly longer and also wider than the opening I8. Adjustable stop screws 25 are mounted on and extend through the pipe I5, having their ends located so that the plate 24 comes thereagainst in the position of the parts shown in- Fig. 3, which prevents complete closure of the air opening I3. X

Gas passes from the pipe II under the lower edge of the vane I9 and is metered by the space between the lower edge of the vane and the adjustable plate 26. The plate 26 is hinged at 21 to the forward side of the box I5a, the hinge being located so that the lower edge of the vane I9, when swung suiiiciently, will engage it to The vane completely close the opening under the Wine; The plate inclines downwardly and may haveits movable edge rest against the bottom of the box In or its inclination may be altered by raising its movable edge by means of adjusting screws 28 whereby the passage space imder the vane I9.may be altered. By this construction a gradual variation of the gas passage occurs by swinging the vane I9, which passage varies from extreme opening when the vane is swimg 1 rearwardly toward the pipe 11 to a complete closure when the vane is swung forwardly against the hinge 21.

Fuel is furnished-to the fuel feed pipe I by a fuel pump 30 which is located on the outside 1 of the conduit I5 and the shaft-l3a, which is driven by the motor I3 and carries the fan rotor I4, also operates the fuel pump 30. By this means'the' supply of fuel is automatically provided whenever the motor I3 and the fan I4 2 are in operation and cessation of the operation of these parts automatically stops the feeding of fuel.

Operation While in operation the motor I3 drives the fan I4 which blows air, taken through the opening I8, mixed with the products of .combustion taken from the flue 5 through the pipe I! and passing under the vane I9, which mixture is blown 3 through the conduit II, the housing II and pipe 9 into the combustion chamber whereit mixes with fuel supplied by the pipe I providing a combustible mixture which is ignited by suitable means and burns within the combustion chamber 3 2. The gaseous products of 7 this combustion pass off, a in the particular furnace structure shown, through the downward'passagcs 3 into the flue 5, the smoke pipe 6 connecting with said flue 5 through which a part of the burned gas 4 passes to a chimney and a part of the gas from the flue 5 is drawn, as above described, through the pipe I! and the other parts by the fan I4 to be mixed with air and rebumed.

It is most desirable for even, quiet and safe 4 combustion to maintain a constant substantially flxed proportion of fresh air and burned gas during normal operating conditions and this proportion is eifectively maintained byoperation bf the present device. The suction produced by'o the fan I4, when it is in full motion, is constant and the pressure of the fresh air causing it to pass through the opening I8 is also constant but the pressure of the burned gas in the-flue 5 varies greatly because of the different forces acting 5 upon it. e

The draft in the chimney, to which the smoke pipe 6 is connected, will vary because of outside weather conditions including temperatures, wind conditions, humidity, etc., and the heat of the 3 chimney and smoke pipe will also have its effect upon the draft created. Fluctuations in the flame, called flame pulsations, decidedly affect the pressure in the flue 5 and other forces may act to alter the pressure in the flue. I! The vane I9 controls the quantity of'burned gas drawn from the flue 5 by the fan I 4, this gas passing under the vane and between its lower edge and the plate 26 and the opening between the vane and the plate 26 controls the quantity of 7 gas permitted to pass. The suction produced by the fan acts upon the vane I9 tending to swing it toward the hinge stop 21 such movement being -resisted by the weight 22,and suction within the flue 5 acts oppositely upon the vane to move it 7i in the other directiomsuch action being aided by the weight 22.

with a constant suction produced by the fan, the variable suction or pressure in the'flue causes a movement of the vane to control the .passage of gas past it. The condition of the gas in the flue 5 may be termed as pressure with the understanding that such pressure may be either greater or less than atmospheric pressure dependingupon the draft existing in the chimney, and smoke pipe 6. Under certain conditions, especially whenthe chimney and smoke pipe are cold, substantially no draft will exist and pressure created in the'combustion chamber 2 will be transmitted to the flu'e 5 causing .a pres.- sure above atmospheric in saidflue'while at other, times when a relatively strong draft exists the pressure within the flue 5 will be lessthan atmospheric pressure. I With a high pressure in the flue 5 the fanwould ordinarily draw an excessive amount-of. burned gas to be mixed with the air for 'combustion-but such pressure in the flue acts upon the vane IS, in conjunction with the suction of the j fan acting upon the vane, causing, the vane to move toward the stop 21 to reduce the size of the passage. A low pressure in the flue 5 has the natural effect to resist movement caused bysucpressure in the flue and the passage opening past the vane increased the gas willflow through the increased passage at a lower speed.

Fluctuation of the vane l9 causes correspond- 1 ing fluctuation of the closure plate 24 at the fresh air opening- I8, movement of the plate 24' being in a direction to provide a larger opening for the passage of air with movement of the vane- IS in a direction to restrict the size of the gas passageway.

The device is adjusted'i'or operation by deter-- mining the average normal positions of the air valve 24' and the gas vane l9 under draft conditions existing in that particular installationjv and the stop screw .25 is moved to a position to,engage the valve plate 24 when it has moved t'oward closed position somewhat beyond the average normal position. JI'he lever 2|, with -its weight 22, is rotatably adjusted on the shaft 20 so that itiwill exert the proper effort required in that particular installation to resist closing movement of the vane.

It will be noted that when the lever Misadjusted on the shaft 20 to stand in a substantially and Supplied to the fire, the vflame assumes a horizontal position, as shown in Fig. 3, the effort of the weight 22 to swing the vane I9 is substantially constant throughout the arc in which-it moves. If the lever 2| is adjusted on the shaft 20 to extend'downwardly as in Fig. 5 the effort of the weight to resist closing movement of the vane increases as the vane swings toward :closed position while if the lever is adjusted on the shaft to extend upwardly as shown in Fig. 4, the effort of the weight to resist closing movement of the vane decreases as the-vanemoves' toward closed position; Adjustment of the weight 22 lengthwise of the lever 2| governs the amountof effort exerted in any of the positions of the.) lever.-'

The plate26 is adjustedby the screws 28 to govern the maximum gas passage between it" and the lower'edge of the vane It. This plate extends tangentially from the arc inwhich the lower edge of the vane swings and therefore movement of the vane toward the point of con-v vergence between its arc and the plate reduces the distance between, the lower edge of the .v'ane and the plate.

'With the parts properly adjusted asubstantiaily constant proportion of air through the opening [8 and burned gas through thelpipe i1 issupplied by the fan I! to thecombustion chamber where it is mixed with fuel oil from the pipe ,I to be'burned. Under normal conditions the vane I9 is affected by change in pressure in the gas flue 5 causing it to swing from oneposition to'another' increasing or decreasing the gas passage beneath' its lower edge and at the same that they-will maintain a substantially co'nstant proportion of burned gas andair during'norm'al running conditions and will not permit the passage or gas in sufficient quantity-to extinguish the'flame. In cases 'of abnormal gas flue' pressure, which can be caused by extreme flain'epultime moving the plate 24 and inversely varying sations or other causes, the vane l9 moves against thehinge stop 2'! completely closing the gas passage "and opening the'air passage to its fullest extent'whereby only fresh air is admitted to the flame which will cause it for the instant during such abnormal pressure to become luminous I which is the safest'burning condition.

Sincethis apparatus is especially adapted to be used in automatic thermostatically controlled on burning 'fumaces in. which combustion occurs at intermittent intervals and in which there are frequent ignition periods, the device is arranged to facilitate the ignition of the fuel at each ignition fperiod. After thej' flame has been extinguished -for some time the gas flues and combustion chamber of the furnacewill have exhausted all "of the burnedigas therein into the smoke stack and will containsubstantially fresh air. Therefore. at the. time .o fjignition only'fresh air can be suppliedto the fuel whichqprovides the best 'mixture to assure ignition and fresh 'air continues to be supplied, both through the air opening l8 and past; the vane 19 for an appreciable period until the burnedgas of combustion has had time to circulate from thecombustion chamber through the gas passages and back to the flame which period is sufficiently long to assure establishment ofcombustion. As soon as burned gas from the combustion chamber has circulated through the gas 'flues so that item pass the vane I 9 to "be mixed with air in the conduit l5 blue condition and the device automatically acts to maintain this condition under normal condithat the automatic control of the recirculation of burned gas to'the fire actuated by differences in" draft pressure Imayb'e utilized without the simultaneous variation of the fresh air supply.

The invention is defln'edi'n the appended claims and is to be considered comprehensive of all forms of structure coming within their scope.

I claim:

1. The combination with a furnace having a combustion chamber and a flue connected with a smoke pipe in all of which varying pressure occurs and to which gases of combustion are delivered, of aconduit communicating with said combustion chamber, means for forcing an air current in said conduit and into said combustion chamber, a communicating passage between said conduit and said burned gas flue, a movable valve member in the burned gas passage and affected by variations in pressure in said flue to be moved toward either open or closed position, valve means for admitting fresh air into said conduit actuated by said gas valve means to be moved toward open position when the gas valve means moves toward closed position and vice versa.

2. The combination with a fuel burning combustion chamber having a horizontal flue to which gases of combustion are delivered and a smoke pipe connected with said flue, of a vertical conduit connected at its upper end with the front part of said combustionchamber, a horizontal pipe connecting the lower end of said conduit with said flue, said vertical conduit having an air entrance opening in a vertical side thereof, a plate located at the outer side of said opening, a rod connected to said plate, extending through said opening and downwardly adjacent said flue, a

vane mounted to turn upon a horizontal axis mounted in said horizontal pipe adjacent the flue, the lower end of said rod being connected with said vane and a blower in said conduit above said vane and air entrance opening.

3. A construction containing the elements in combination defined in claim 2, combined with means carried by said conduit to engage against .said plate to limit the extent of movement of said plate toward the conduit and thereby prevent complete closure of said air entrance opening.

4. In combination with a horizontal fuel burning combustion chamber, a horizontal flue below said combustion chamber to which gaseous products of combustion are delivered, a smoke pipe connected to the flue, a vertical conduit having mounted on said arm, aplate larger than the airentrance opening located at the outer sideof the-flue in a position to cover said opening, a rod secured at one end to said plate and at the other end to said vane a short distance below said shaft, and a motor driven blower located in said conduit above said vane and air entrance opening.

5. A construction containing the elements in combination defined in claim 4, combined with adjusting screws on the conduit and having ends bearing against the inner side of said plate.

6. A construction containing the elements in combination defined in claim 4 combined with stop means located in the lower portion of said conduit opposite the lower portion of said vane, said stop means extending substantially across the full widthof the conduit in the path of movement of the lower portion of the vane.

7. The combination with a furnace having a.

combustion chamber, of means for mixing gases of combustion with air comprising, a conduit for carrying a portion of the gases of combustion back to the entrance of the combustion chamber,

a blower in saidconduit, said conduit having an air entrance opening, a closure for said opening, obstructing means across the conduit partially obstructing the passage of said gases of combustion, said obstructing means being movably mounted and automatically movable to different 1 positions to permit the passage of a greater or less quantity of the gases of combustion, and connections between said obstructing means and air inlet closure means causing the same to move simultaneously.

8. A construction containing-"the elements in I combination defined in claim '7, combined with means located in said conduitin cooperation with said obstructing means for limiting or prohibiting the passage of gases of combustion to said conplying burned gas from said flue to said com- 1 bustion chamber and means subjected to pressure in said flue and stack and actuated by variations thereof for maintaining substantially constant the proportions of air and burned gas supplied to said combustion chamber during norl mal operation.

10. The combination with a furnace having a combustion chamber and a flue connected with a smoke pipe to which gases of combustion are delivered from the combustion chamber, of a conduit, in which varying pressure occurs, in communication with said flue, means for forcing the contents of said conduit therefrom into said combustion chamber, valve means for admitting undiluted fresh air into said conduit, valve means for admitting gases of combustion into said conduit, means for operatively connecting the gas valve means to the air valve means, said last mentioned valve means being actuated by variations in pressure in said flue for automatically actuating said air valve means whereby a substantially constant proportion of fresh air and gas is admitted to said conduit.

11. The elements in combination defined in claim locombined with means for independently adjusting the gas valve means. 7

12. The elements in combination defined in claim 10 combined with adjustable means for limiting the closing of the air valve means.

13. The combination with a furnace having a combustion chamber and a flue to which gases of combustion are delivered, of a conduit connecting one end of said flue with the entrance end of the combustion chamber, a blower in said conduit, a vane movably mounted in the conduit across the same between said blower and flue to partly obstruct passage of gases of combustion to said blower, said conduit having an air entrance opening therein, a plate to open or close said opening, and connections between the vane and plate to automatically and simultaneously open said air entrance opening to a greater degree and limit the passage of gases of combustion to a correspondingly lesser degree.

14. The combination of elements as set forth varying pressure progressively moving the valve means toward and from its closed position where- 'by a lesser or greater opening is aflorded for the said portion of the products of combustion to pass thereby.

16. The combination of elements set forth in claim 15, in which means is provided to admit a supply of fresh air at atmospheric pressure to the conduit between the valve means and the combustion chamber.

10 DONALD J. Lu'rr. 

